YANGON, Myanmar (AP) - An explosion struck one of the most prestigious hotels in Myanmar's main city just before midnight on Monday, ripping apart a guest room and wounding one American - the latest in a series of unexplained blasts to hit the Southeast Asian country.

It was not immediately clear what caused the explosion at the 22-story Trader's Hotel in downtown Yangon. But the incident came after unidentified assailants planted several homemade bombs across the country in recent days, reportedly killing two people outside the city and injuring three others in Yangon on Sunday.

There was no visible damage to exterior of the hotel early Tuesday, but the explosion shattered part of one room on the ninth floor of the building, leaving shredded toilet paper, towels and a red purse scattered across the room's entranceway beside a broken wooden wardrobe door that had collapsed.

A 43-year-old American woman was slightly injured and taken to a Yangon hospital, according to a police officer on the scene who declined to be named because he was unauthorized to speak about the incident. He said the blast occurred in or near the room's bathroom, and the woman's husband and two children were unhurt.

An American Embassy official confirmed that one American was injured and taken to a Yangon hospital, but gave no other details and declined to say whether the explosion was caused by a bomb.

A dozen police and soldiers with a sniffer dog entered the hotel. Later, many of them crowded into the destroyed room to inspect the damage. The room was blocked off with security tape, shards of glass littered the road outside.

Small explosions occurred frequently when Myanmar was under 50 years of military rule, most often blamed on anti-government student activists or armed ethnic insurgent groups. But such incidents have become rare in recent years.

Myanmar has undergone rapid change since 2011, when the former army junta ceded power to a quasi-civilian government led by retired military officers. Since then, President Thein Sein has embarked upon a series of major reforms, liberalizing the economy and the political sphere, easing censorship and freeing political prisoners.

But many activists and rights groups have complained that country is still far from free, and dissent is frequently stifled. Thein Sein's government has also struggled both to end a civil war with ethnic Kachin rebels in the north, and curb a rising wave of anti-Muslim violence that has killed hundreds of minority Muslims and displaced nearly 150,000 more in the predominantly Buddhist country since last year.

No one claimed responsibility for the recent blasts to hit the country, which came as the country prepares to host the Southeast Asian Games in December.

The first bomb reportedly went off Friday at a guesthouse in Taungoo, a town 200 kilometers (125 miles) from Yangon, according to the independent media outlet, the Democratic Voice of Burma. It said two people were killed, but those casualties could not immediately be confirmed.

On Sunday, two other homemade bombs went off in Yangon. One of the bombs, attached to the bottom of a truck parked outside a market on Yangon's eastern side, wounded three civilians, according to a statement posted on Myanmar's police Facebook page.

Another homemade bomb exploded one at a bus stop in the west of the city, but no casualties were reported in that blast, police said.

Police called on the public to be vigilant and report any suspicious packages found at bus or train stations, or at the seaport.